Water – Very low water pressure in the 2nd floor shower but good pressure every where else

Here are the facts:

• I have a 2 or 2.5 inch water pipe from the street and supposedly very high water pressure.

• This is the master shower and is located on the second floor.

• It was remodeled 11 years ago, we do not know how the pressure was before.

• The water pressure for the kind of shower-head I had purchased was disappointing even at the time the work was just finished but acceptable. The plumber said something about the restrictor in the shower head, I removed-it did not improve. I let it be since the water pressure was acceptable.

-Over the years the water pressure got less and less, similarly the water temp was reduced noticeably.

• However, the tub in the same bathroom has an incredible pressure and gets very hot. Sink faucets work well.

• Other showers in the house work well.

• Brought in one plumber who took out the sensor valve and cleaned it. It did not improve anything.

• The second plumber took out the same valve and found some debris in the pipe leading into it. And using the screws next to the sensor it increased the pressure of hot water. What we noticed is that the hot water pressure coming out of the pipe (without any sensor involved) is considerably low compared to cold water pressure.

• Although both pressure and temp are now better, both are below optimal. My quesion is why, is it that the hot water going into the shower somehow is clogged up or is it that the plumber used the wrong diameter tubing in the rough work behind the shower wall?